Research projects are designed to further the knowledge about the development and differentiation of the sensory epithelia of the inner ear and the mechanisms involved in normal and abnormal development. The embryonic chick is being used as a model for these studies on the basilar papillae and cristae. In order to obtain adequate information several techniques are being used: Organ culture, electron microscopy, histological preparations histochemical and differential stains. There are three areas of investigation. 1. The development of the otocyst and acoustic ganglion in the embryonic chick and quail. 2. The characterization of the development of the sensory epithelia of the inner ear in vivo and in organ culture at the three phases of embryonic development: Phase 1. Localization of presumptive sensory epithelia; Phase 2. The mid-point in morphogenesis of sensory structures and cytodifferentiation of hair cells; and Phase 3. The completion of morphogenesis of the sensory structures and cytodifferentiation of cells of the sensory epithelia.